Isolator Base GSA-IB, GSA-IB4 - This base includes a built-in line fault isolator for use on Class A circuits. A detector must be installed for it to operate. The isolator base does not support the GSA-LED Remote LED. The process repeats beginning on the other side of the loop controller. All detector mounting bases have wiring terminals that are accessible from the “room-side” after mounting the base to the electrical box. The bases mount to North American 1-gang boxes and to 3 1⁄2 inch or 4 inch octagon boxes, 1 1⁄2 inches (38 mm) deep. They also mount to European BESA and 1-gang boxes with 60.3 mm fixing centers. The GSA-SB4, GSA-RB4, and GSA-IB4 mount to North American 4 inch sq. electrical boxes in addition to the above boxes. They include the GSA-TS4 Trim Skirt which is used to cover the “mounting ears” on the base. The GSA-AB4G mounts to a 4” square box only.